The present invention relates to internal combustion engines, and, more particularly, to a method of controlling detonation in internal combustion engines.
An internal combustion engine generally is of two basic types, i.e., a spark ignition engine and a compression combustion engine. A spark ignition engine uses a spark plug to ignite the fuel and air mixture which is injected into the combustion chamber. A compression combustion engine utilizes the energy resulting from compression of the fuel and air mixture as the piston travels towards a top dead center position within the combustion cylinder to ignite the fuel and air mixture. Regardless of whether the internal combustion engine is a spark ignition engine or a compression combustion engine, it is desirable to control the point in time at which combustion occurs relative to the position of the piston within the combustion cylinder.
It is known to provide a plurality of pressure sensors which sense pressures within respective combustion cylinders at discrete points in time. Signals from the pressure sensors may be transmitted to an Electronic Control Module (ECM) for the purpose of controlling the timing of the combustion event within the combustion cylinder as the piston reciprocates between a bottom dead center position and a top dead center position. Sensing pressures within combustion cylinders for the purpose of controlling the timing of the engine is disclosed, e.g., in U.S. Pat. No. 4,063,538 (Powell et al.), U.S. Pat. No. 4,736,724 (Hamburg et al.); U.S. Pat. No. 5,276,625 (Nakaniwa); and U.S. Pat. No. 5,359,833 (Baldwin et al.). Examples of pressure sensors which withstand the harsh operating environment in a combustion cylinder are disclosed in U.S. Pat. No. 5,714,680 (Taylor et al.); U.S Pat. No. 5,452,087 (Taylor et al.); and U.S. Pat. No. 5,168,854 (Hashimoto et al.).
It is also known to utilize a pressure sensor within a combustion cylinder for the purpose of reducing engine detonation or knocking. Detonation occurs when an exothermic chemical reaction propagates with such a high speed that the rate of advance of the reaction zone into the unreacted fuel and air mixture exceeds the velocity of sound in the fuel and air mixture; that is, the advancing reaction zone is preceded by a shock wave. Pressure sensor signals are analyzed to determine whether high frequency variations in the cylinder pressure due to engine detonation are occurring. If detonation is occurring, the spark advance in the spark ignition engine is adjusted to assure that peak cylinder pressure occurs at the optimum crank angle consistent with desired reduction in engine detonation. An example of utilizing pressure sensor signals in a combustion cylinder for the purpose of reducing engine knock is disclosed in U.S. Pat. No. 4,620,438 (Howng).
A problem with a method as described in the Howng ""438 patent as described above is that only the occurrence of detonation is detected using the pressure sensors. If any detonation is detected, the spark advance of the engine is adjusted. However, not all detonation is deleterious to efficient operation of the internal combustion engine. Thus, by adjusting operation of the internal combustion engine upon occurrence of any detonation, unnecessary and therefore inefficient adjustments of the internal combustion engine are effected.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the invention, a method of controlling detonation in an internal combustion engine is provided with the steps of: combusting a fuel and air mixture within a combustion cylinder; sensing a plurality of pressures at discrete points in time within the combustion cylinder; determining a pressure profile of the plurality of pressures; detecting detonation within the combustion cylinder; and acting upon the detonation, dependent upon where the detonation occurs on the pressure profile.